kernel/*: switch to memdup_user_nul()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 7 insertions, 14 deletions

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 88fefa68c516..9bafc211930c 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -602,8 +602,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	struct uid_gid_map new_map;
 	unsigned idx;
 	struct uid_gid_extent *extent = NULL;
-	unsigned long page = 0;
-	char *kbuf, *pos, *next_line;
+	char *kbuf = NULL, *pos, *next_line;
 	ssize_t ret = -EINVAL;
 
 	/*
@@ -638,23 +637,18 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
 		goto out;
 
-	/* Get a buffer */
-	ret = -ENOMEM;
-	page = __get_free_page(GFP_TEMPORARY);
-	kbuf = (char *) page;
-	if (!page)
-		goto out;
-
 	/* Only allow < page size writes at the beginning of the file */
 	ret = -EINVAL;
 	if ((*ppos != 0) || (count >= PAGE_SIZE))
 		goto out;
 
 	/* Slurp in the user data */
-	ret = -EFAULT;
-	if (copy_from_user(kbuf, buf, count))
+	kbuf = memdup_user_nul(buf, count);
+	if (IS_ERR(kbuf)) {
+		ret = PTR_ERR(kbuf);
+		kbuf = NULL;
 		goto out;
-	kbuf[count] = '\0';
+	}
 
 	/* Parse the user data */
 	ret = -EINVAL;
@@ -756,8 +750,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	ret = count;
 out:
 	mutex_unlock(&userns_state_mutex);
-	if (page)
-		free_page(page);
+	kfree(kbuf);
 	return ret;
 }